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Phylum Mollusca > Class Gastropoda > sea slugs > Order Nudibranchia
Blue dragon nudibranch
Pteraeolidia ianthina
Family Facelinidae
updated Jun 2023
Where seen? This brilliant nudibranch is often seen on many of our shores, in coral rubble and near reefs. It is also commonly seen by divers.

3-5cm. Long, narrow, soft body with finger-like projections (called cerata) arranged in hand-like clusters along the length of the body. Those encountered were mostly blue, sometimes also mostly brown with blue tipped cerata. Elsewhare, various colours are reported from yellow to green. It is identified by the purple bands on its long oral tentacles. It has a pair of shorter feathery rhinophores.

A recent study suggests this species comprises a cryptic species complex, with what is currently perceived as a single species actually being multiple genetically-distinct species that look almost indistinguishable to the naked eye.

Beting Bronok, Aug 05

Purple bands on oral tentacles.

Feathery rhinophores.

Pulau Sekudu, May 12

Cerata in hand-like clusters

Laying egg string on seagrass.
Lazarus (Eagle Bay), Nov 22
Photo shared by James Koh on facebook

Laying egg string on seagrass.
Lazarus (Eagle Bay), Nov 22
Photo shared by James Koh on facebook
What does it eat? It eats hydroids. A large solitary hydroid, Ralpharia sp. is among the adult's favourite food. Young ones have been seen among short 'turfing' hydroids. The blue dragon nudibranch can also store symbiotic algae (zooxanthellae) within its cerata and body. Here, the zooxanthellae get protection and in turn provides the nudibranch with much of the nutrients produced through photosynthesis. Young animals are white as they have yet to develop their crop of zooxanthellae. Older ones may be brown. Adults often can go without feeding for sometime, possibly living off the nutrients provided by the zooxanthallae.

Pteraeolidia species have a habit of staying near their eggs once they've laid them. Several individuals may stay near the eggs for several weeks. But it is not clear whether they are actually caring for their eggs.

Blue dragon nudibranchs on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Pulau Sekudu, May 12
Photo shared by James Koh on flickr.

Pulau Sekudu, Jul 15

Photo shared by Rene Ong on facebook.

Beting Bronok, Jun 10
Photo shared by Loh Kok Sheng on his blog.

East Coast Park (B), Jun 21

Photo shared by Loh Kok Sheng on facebook.

Sentosa Serapong, Dec 20

Photo shared by Vincent Choo on facebook.

Small Sisters Island, May 18

Photo shared by Abel Yeo on facebook.

Pulau Jong, Aug 20

Photo shared by Loh Kok Sheng on facebook.

Cyrene Reef, Nov 08

Photo shared by Marcus Ng on flickr.

Cyrene Reef, Jun 17

Photo shared by Toh Chay Hoon on facebook.

Cyrene Reef, Apr 08
Photo shared by Toh Chay Hoon on flickr.

Pulau Semakau East, Jan 16
Photo shared by Loh Kok Sheng on facebook.

Pulau Semakau, Jun 08

Photo shared by Loh Kok Sheng on his flickr.

Terumbu Raya, May 10

Photo shared by Toh Chay Hoon on her blog.

Terumbu Semakau, Jun 12

Photo shared by Russel Low on facebook.

Pulau Salu, Apr 21

Photo shared by Jianlin Liu on facebook.

  • Nathaniel Soon, Z B Randolph Quek, Sebastian Pohl, Benjamin J Wainwright. "More than meets the eye: characterizing the cryptic species complex and Symbiodiniaceae communities in the reef-dwelling nudibranch Pteraeolidia ‘semperi’ (Nudibranchia: Aeolidioidea) from Singapore" Journal of Molluscan Studies, Volume 89, Issue 2, June 2023,
  • Tan Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist of The Molluscs of Singapore (pdf), Raffles Museum of Biodiversity Research, National University of Singapore.
  • Debelius, Helmut, 2001. Nudibranchs and Sea Snails: Indo-Pacific Field Guide IKAN-Unterwasserachiv, Frankfurt. 321 pp.
  • Wells, Fred E. and Clayton W. Bryce. 2000. Slugs of Western Australia: A guide to the species from the Indian to West Pacific Oceans. Western Australian Museum. 184 pp.
  • Coleman, Neville. 2001. 1001 Nudibranchs: Catalogue of Indo-Pacific Sea Slugs. Neville Coleman's Underwater Geographic Pty Ltd, Australia.144pp.
  • Coleman, Neville, 1989. Nudibranchs of the South Pacific Vol 1. 64 pp.
  • Gosliner, Terrence M., David W. Behrens and Gary C. Williams. 1996. Coral Reef Animals of the Indo-Pacific: Animal life from Africa to Hawai'I exclusive of the vertebrates Sea Challengers. 314pp.
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